Wireless communication systems are widely used to provide voice and data services for multiple users using a variety of access terminals such as cellular telephones, laptop computers and various multimedia devices. Such communications systems can encompass local area networks, such as IEEE 801.11 networks, cellular telephone and/or mobile broadband networks. The communication system can use one or more multiple access techniques, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and others. Mobile broadband networks can conform to a number of standards such as the 2nd-Generation (2G) technology such as Global System for Mobile Communications (GSM) and/or the like, the 3rd-Generation (3G) technology such as Universal Mobile Telecommunications System (UMTS) and/or the like, and the 4th-Generation (4G) technology such as Long Term Evolution (LTE) and/or the like.
A wireless network may include a plurality of wireless devices and a plurality of base stations. The wireless devices may be notebook computers, mobile phones or Personal Digital Assistant (PDA) devices, media players, tablet computers, large format mobile phones, digital readers, gaming devices, and various combinations thereof and/or the like.
The base stations communicate with the wireless devices over a plurality of wireless channels coupled between the wireless device and the base stations (e.g., a downlink channel from a base station to a wireless device). The wireless device may send back information, including channel information, to the base stations over a plurality of feedback channels (e.g., an uplink channel from the wireless device to the base station) in a manner that provides service to a desired coverage area, without contributing undue interference.
Power amplifiers are important components in the base stations of a wireless network. High efficiency and high linearity power amplifiers are desirable in order to improve the performance of a wireless communication system.
As wireless techniques further advance, outphasing amplifiers have been employed to improve efficiency and linearity of an amplitude-modulated radio frequency system. In a wireless system having outphasing amplifiers, an amplitude-modulated signal is decomposed into two phase-modulated signals by a signal component separator. These two phase-modulated signals are of the same envelope while having opposite phase variations. Such two constant-envelope signals are amplified by two separate amplifiers to produce two amplified signals, which are sent to a power combiner and are combined at the output of the outphasing amplifier to form an amplified replica of the original amplitude-modulated signal.